1. Field of the Invention
The present invention relates to an active matrix liquid crystal display (LCD) apparatus, and more particularly, to an active matrix LCD apparatus for displaying images of different magnifications.
2. Description of the Related Art
Usually, in a first prior art active matrix LCD apparatus, the number of scanning lines is fixed. This will be explained later in detail. Therefore, when a television image having a small number of scanning lines is displayed on the active matrix LCD apparatus, an interpolation operation is carried out to increase the number of scanning lines. This is complex to control.
In a second prior art active matrix LCD apparatus (see JP-A-62-138893), a clock multiplexing circuit is provided between a controller and a gate line driving circuit for driving gate lines. Therefore, a clock signal obtained by the clock multiplexing circuit is formed by pulse groups each including two or more pulses, and the period of the pulse groups is equal to a one line scan time period. As a result, two or more of the gate lines are approximately simultaneously driven. Thus, the displayed area of the LCD panel in the longitudinal direction can be enlarged. This also will be explained later in detail.
In the second prior art apparatus, however, since the magnification of the displayed area in the longitudinal direction is an integer, the displayed area may be too much smaller or too much larger than the LCD panel, in other words, the displayed area hardly coincides with the LCD panel.
In a third prior art active matrix LCD apparatus (see JP-A-5-100640), the outputs of D flip-flops of the gate line driving circuit are connected to buffers via clocked inverters instead of the clock multiplexing circuit of the second prior art apparatus. This also will be explained later in detail.
In the third prior art apparatus, however, although-the magnification of the displayed area in the longitudinal direction can be arbitrary, this magnification is fixed. Also, the clocked inverters increase the manufacturing cost. Further, a write operation cannot accurately be carried out for the apparatus which is of a gate storage type where a storage capacitor is formed on an adjacent gate line.
In a fourth prior art active matrix LCD apparatus (see JP-A-5-303362), switches are provided instead of the clocked inverters of the third prior art apparatus. This will also be explained later in detail.
In the fourth prior art apparatus, however, although the magnification of the displayed area in the longitudinal direction can be arbitrary, this magnification is fixed. Also, the switches increase the manufacturing cost. Further, the maximum magnification is 2, and therefore, it is impossible to obtain a magnification larger than 2.